1. Field of the Invention
The present invention relates to a power generator, and more particularly, to a power apparatus and method thereof to provide a high voltage by which a user varies power supplied by a power generator according to an externally-applied input.
2. Description of the Related Art
FIG. 1 is a block diagram illustrating a structure of a conventional power apparatus to provide a high voltage. Referring to FIG. 1, the conventional power apparatus to provide the high voltage includes a pulse width modulation (PWM) inputting unit 100 which receives a signal PWM from a CPU (not shown) so as to output an AC high voltage, a comparator 101 which compares the PWM signal with a reference potential, a switching controller 102 which forms a compared output signal to a V2 potential, a TRANS 103 which converts the output signal of the switching controller 102 into the high voltage, and a final outputting unit 104 which outputs the high voltage-converted signal.
If the signal PWM is inputted to the comparator 101 from the CPU, the comparator 101 compares the signal PWM with the reference potential that is divided by resistors R3 and R4, and generates the compared output signal. The compared output signal has the same shape as that of the signal PWM, and the switching controller 102 generates a signal having the V2 potential by performing an ON/OFF operation of a transistor Q1 in response to the compared output signal. Thereafter, the signal generated by the switching controller 102 is amplified by the TRANS 103 and output through a final output terminal of the final outputting unit 104.
The conventional power apparatus to provide the high voltage amplifies the inputted PWM signal and supplies the amplified PWM signal to a development unit, with a duty cycle (%), which varies with the CPU. However, as shown in FIG. 2, an AC output potential Vp-p is fixed according to the reference potential that is set to the resistor R3 and the resistor R4. In order to adjust the output potential, a variable resistor should be connected to the resistors R3 and R4 such that the reference potential can be varied. When the apparatus is in operation, it is impossible to automatically vary the resistors R3 and R4. In the case of a mono laser beam printer, a fixed output with the AC high voltage can be adapted to the conditions of a development process. In the case of a color laser beam printer, due to a more complicated process environment and conditions, a power apparatus by which a user voluntarily varies the AC output potential Vp-p is required.